The acceptance of alternative toxicological test methods by regulatory agencies is determined by their reliability and relevance for a given purpose, i.e. whether the test method has been validated. If a test for genotoxicity can be selected according to toxicological principles so that, in concert, they detect the full range of mutagenic events that could ultimately lead to cancer, then theoretically the test optimal predictive of carcinogenicity will have been selected. The purpose of this Phase II project is to validate the new lacZ plasmid-based transgenic mouse mutation assay. These transgenic mice carry multiple copies of a plasmid, containing the bacterial lacZ marker gene, integrated head-to-tail in the genome of all organs and tissues. Highly efficient protocols for the rescue of these vectors from their integrated state have been developed. The detection of mutations in the lacZ reporter gene is facilitated by a positive selection system. Our approach would be to correlate mutagenicity with tumor formation in a selected number of target and non-target tissues following exposure to these chemicals. This should help to define the measure of relevance of the plasmid-based transgenic mouse mutation assay such as operational characteristics (sensitivity, specificity), statistically derived correlation coefficients, and determinations of the mechanistic association of the measured effect (mutant frequency) with the toxic event of interest (carcinogenicity). PROPOSED COMMERCIAL APPLICATION: Validation of this new lacZ-plasmid-based transgenic mouse model will help to position this model as a definitive model for toxicological testing of new pharmaceuticals, chemicals etc. When accepted as such by governmental regulatory agencies, it will greatly increase the sales of kits Leven is currently selling for this system.